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71.
The mature winter leaves of Pilosella officinarum coll. Schultz and Schultz contained 29 mg esterified triterpenoid alcohols (g dry weight)−1 , of which over 80% was esterified with long-chain (C16-C18) fatty acids. The major fatty acids were 16:0, 18:2ω6 and 18:3ω3 and their amounts varied according to the season and stage of leaf development. In mature leaves the amount of triterpenoid alcohols esterified with long-chain fatty acids varied only slightly with the season. The changes in the fatty acid proportions in late winter-early spring, however, indicated a turnover in the esterified triterpenoid alcohol pool. In late winter after the snow had melted a 50% decrease occurred in the amount of triterpenoid alcohols esterified with short-chain fatty acids. The amount of esterified triterpenoid alcohols in immature leaves was relatively low [4 mg (g dry weight)−1 ].
In the mature leaves esterified triterpenoid alcohols were found in globules whose appearance varied greatly according to the season. The globules were partly dissolved in late winter, and this together with the activation of respiration, suggests that the globules function as short-term energy reservoirs. Relationships between the appearance of lipid globules and the amount of esterified triterpenoid alcohols are discussed. 相似文献
In the mature leaves esterified triterpenoid alcohols were found in globules whose appearance varied greatly according to the season. The globules were partly dissolved in late winter, and this together with the activation of respiration, suggests that the globules function as short-term energy reservoirs. Relationships between the appearance of lipid globules and the amount of esterified triterpenoid alcohols are discussed. 相似文献
72.
水稻叶片中存在着氨肽酶,其最适反应pH和最适反应温度分别为8.2℃和40℃,酶促反应的产物量在最初30min内与时间呈直线相关。 水稻叶片衰老过程中叶绿素和蛋白质含量下降,而氨肽酶比活上升;用植物激素延缓或促进叶片衰老蛋白质降解的同时也抑制或促进了氨肽酶比活的上升,说明氨肽酶在水稻叶片衰老蛋白质降解过程中起一定的作用。根据水稻叶片衰老过程中大分子化合物和叶片外部形态的变化,可将叶片衰老过程划分为缓衰期、急衰期和竭衰期。 相似文献
73.
P. Fleurat-Lessard 《Protoplasma》1986,130(1):1-4
Summary Parenchyma cells ofMimosa pudica display close associations between two or more cisternae of the endoplasmic reticulum. These associations form simplified types of lamellar bodies in which inner paired lamellae have lost their ribonucleoprotein granules and are separated by a dense layer. 相似文献
74.
A. N. WEBBER N. R. BAKER CANDIDA D. PAIGE M. F. HIPKINS 《Plant, cell & environment》1986,9(3):203-208
Abstract Photosynthetic electron transport activities and the ability to generate and maintain a trans-thylakoid proton electrochemical gradient were examined during chloroplast development in 4-day-old wheat leaves grown under a diurnal light regime. Polarographic and spectropholometric studies on leaf tissue demonstrated that poorly developed chloroplasls at the leaf base could photo-oxidize water and transfer electrons from photosystem 2 to photosystem 1. The capacity for non-cyclic whole-chain electron transport increased during chloroplast development. Thylakoids isolated from the leaf base, although capable of pumping protons into the inlrathylakoid space, could not maintain a trans-membrane proton electrochemical gradient; this ability developed at later stages of chloroplast biogenesis in the leaf. The implications of these results for the energetics of the developing leaf are discussed. 相似文献
75.
6-(2,3,4-Trihydroxy-3-methylbutylamino) purine, trivial name trihydroxy-zeatin (THZ), an oxidation product of zeatin was applied via the epidermis or cut end of Avena leaf segments. THZ did not retard senescence of the segments in either case. With epidermal application THZ remained unmetabolised while the cut end method of application resulted in its metabolism to more polar THZ metabolites of unknown identity. The Avena leaf tissue did not apparently cleave the isoprenoid side chain of the THZ molecule. 相似文献
76.
The photosynthetic capacity of detached leaves of a non-yellowing mutant of Festuca pratensis Huds. declined during senescence at a similar rate to that in a normal cultivar. Respiratory oxygen uptake in the dark continued at similar rates in both genotypes during several days of senescence. In chloroplasts isolated from leaves at intervals after excision, the rate of photosystem I (PS I)-mediated methyl viologen reduction using reduced N,N,N,N-tetramethyl-p-phenylene diamine as electron donor also declined in both genotypes, possibly due to loss of integrity of the photosynthetic apparatus in the cytochrome f-plastocyanin region. There was a similar fall in PS II electron transport using water as electron donor and measured at the rate of reduction of 2,6-dichlorophenolindophenol. Partial restoration of this activity by the addition of diphenyl carbazide was evidence for lability of the oxygen-evolving complex during senescence. An accentuated difference between mutant and normal material in this case indicated that the mutant retains a greater number of functional PS II centres. Changes in the light-saturation characteristics of the two photosystems have been discussed in relation to the organization of the photosynthetic membranes during senescence.Abbreviations and symbols DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- DCPIP
2,6-dichlorophenolindophenol
- DMSO
dimethyl sulphoxide
- DPC
diphenyl carbazide
- MV
methyl viologen
- PS I, PS II
photosystem I, II
- TMPD
N,N,N,N-tetramethyl-p-phenylene diamine 相似文献
77.
The assimilation of nitrate under dark-N2 and dark-O2 conditions in Zea mays leaf tissue was investigated using colourimetric and 15N techniques for the determination of organic and inorganic nitrogen. Studies using 15N indicated that nitrate was assimilated under dark conditions. However, the rate of nitrate assimilation in the dark was only 28% of the rate under non-saturating light conditions. No nitrite accumulated under dark aerobiosis, even though nitrate reduction occurred under these conditions. The pattern of nitrite accumulation in leaf tissue in response to dark-N2 conditions consisted of three phases: an initial lag phase, followed by a period of rapid nitrite accumulation and finally a phase during which the rate of nitrite accumulation declined. After a 1-h period of dark-anaerobiosis, both nitrate reduction and nitrite accumulation declined considerably. However, when O2 was supplied, nitrate reduction was stimulated and the accumulated nitrite was rapidly reduced. Anaerobic conditions stimulated nitrate reduction in leaf tissue after a period of dark-aerobic pretreatment. 相似文献
78.
Whole leaf hydrocarbons of six species of Phacelia were investigated for their variability among natural Californian populations, and for adaptive 相似文献
79.
Ginette Pauly Abdelhamid Yani Louis Piovetti Colette Bernard-Dagan 《Phytochemistry》1983,22(4):957-959
The essential oils of the leaves of Cupressus dupreziana and Cupressus sempervirens were compared. The composition of the hydrocarbon fraction showed a great similarity between the two species. 相似文献
80.
The spectral properties of the leaves of the herbaceous species Brassica oleracea L. var. botrytis L., Cerastum tomentosum L., Petunia hybrida Vilm., and Talinum paniculatum (Jacq.) Gaertn. were examined to see what effect the epidermis had on leaf absorptance, reflectance and transmittance. Removal of the epidermis from the side of the leaf surface being illuminated resulted in increases in leaf absorptance and transmittance, and a decrease in reflectance in the 400–800 nm waveband. Removal of the epidermis from the opposite side of an illuminated leaf (effect was similar in both abaxial and adaxial surfaces) resulted in small decreases in both absorptance and reflectance, and corresponding increases in transmittance. Removal of both the upper and lower epidermis resulted in a marked increase in transmittance, while both leaf reflectance and absorptance were decreased. The results suggest that the presence of the epidermis significantly increases leaf absorptance in the photosynthetic wavebands. 相似文献